[Bebbetufs]

Like I said in another thread I disagree with this assertion. You want the oil at the bottom of the sump to be as free of air as possible. This means that the bottom is the last place the oil should get to to give it as much time to dump air as possible. You want to be filling from the top. Remember that there is a relatively large volume above the horizontal baffle. The baffle represents the original bottom of the pan, and there is quite a lot of oil in there before it even touches the dip stick.

The baffle is there to keep oil from sloshing away from the pickup (green) and to keep it from climbing up the wall. This means that every time the car corners oil will be gushing out the holes in the mantis baffle like small "underoil" geysirs (red arrows). The longer the turn the less efficient the baffle as the oil, especially when hot, will easily escape through these holes and likely through the flaps which never seal completely, (at least not the BMW rubber flaps I have been testing).

As you see from the figure the deciding factor is the height and efficiency of the horizontal baffle, but this requires the horizontal one to let as little oil escape as possible.

I would prefer one way flaps on the horizontal baffle as well to keep the oil in there (red arrows)